The dye images of silver halide color photographic materials are known to fade markedly, depending on the storage conditions, when they are stored for a long period of time in light, and also when they are exposed to light for short periods of time and stored for long periods of time in the dark. In general, the color fading in the former case is called light fading and that in the latter cases is called dark fading, and when color photographic materials are stored semi-permanently as records it is desirable that the extents of light fading and dark fading should be reduced to a minimum and that the overall tri-color balance of the yellow, magenta and cyan dye images should be maintained in the initial state even after fading. However, the extents of light and dark fading differ for each of the yellow, magenta and cyan dye images, and after long term storage the aforementioned overall faded color balance is inevitably destroyed and the picture quality of the dye image inevitably deteriorates.
The extents of light fading and dark fading differ according to the couplers which are used and other factors but, in many cases, the dark fading arises most readily in the case of the cyan dye image, followed in order by the yellow dye image and the magenta dye image, and the extent of the dark fading of the cyan dye image is greater than that of the other dye images. Furthermore, in the case of light fading, the cyan dye image tends to fade most readily, followed in order by the yellow dye image and the magenta dye image, especially in the case of a light source which is rich in ultraviolet rays.
Thus, in order to maintain a good faded color balance between the yellow, magenta and cyan dye images over a long period of time it is necessary to reduce to a minimum the light and dark fading of the cyan dye image, and various attempts have been made in the past with a view to improving light and dark fading properties for this purpose. These past attempts can be broadly classified into two groups, namely those in which novel couplers which can form dye images which have a smaller tendency to fading have been developed and those in which novel additives which prevent fading have been developed.
Many phenolic cyan couplers were known in the past for forming cyan dyes. For example, the 2-[.alpha.-2,4-di-tert-amylophenoxybutanamido]-4,6-dichloro-5-methylphenol disclosed in U.S. Pat. No. 2,801,171 is such that the colored dye formed from it has good resistance to light, but it has the disadvantage of having poor heat resistance.
Moreover, cyan couplers in which the 3-position or the 5-position of the phenol has been substituted with an alkyl group which has 2 or more carbon atoms have been disclosed, for example, in JP-B-49-11572 (U.S. Pat. No. 3,772,002) and in JP-A-60-209735 and JP-A-60-205447, etc. (the terms "JP-A" and "JP-B" used herein signifies a published unexamined Japanese patent application and examined Japanese patent publication, respectively). The heat stability of the cyan image formed from these couplers is somewhat better, but it is still inadequate.
Furthermore, 2,5-diacylaminophenol based cyan couplers which have an acylamino group in the 2-position and in the 5-position of the phenol have been disclosed, for example, in U.S. Pat. Nos. 2,369,929, 2,772,162 and 2,895,826, and in JP-A-50-112038, JP-A-53-109630 and JP-A-55-163537.
These 2,5-diacylaminophenol based couplers are such that the cyan dye image which is formed has good heat resistance, but there are problems with the coloring properties of the coupler, with the light fading properties of the cyan image which is produced, and with yellowing of the unreacted cyan coupler which is caused by light. Furthermore, even better heat resistance is required.
The 1-hydroxy-2-naphthamide cyan couplers are generally inadequate in respect of both light fading and dark fading properties.
Furthermore, the 1-hydroxy-2-acylaminocarbostyryl cyan couplers disclosed in JP-A-56-104333 have good fastness to both light and heat, but the spectral absorption characteristics of the colored image which is formed are undesirable for color reproduction in a color photograph, and there is a further problem in that pink staining is produced by irradiation with light.
Furthermore, the cyan polymer couplers disclosed in U.S. Pat. No. 3,767,412 and in JP-A-59-65844 and JP-A-61-39044, etc. certainly have excellent heat resistance under dry conditions but their heat resistance is poor under conditions of high humidity and they have a further disadvantage in that their coloring properties are inadequate.
Furthermore, methods in which hydrophobic substance soluble couplers such as oil soluble couplers are dissolved in water miscible organic solvents and the solutions are mixed with loadable polymer latexes and the said hydrophobic substances are loaded onto the polymers have been disclosed in U.S. Pat. No. 4,203,716, etc. However, there is a problem with methods of this type in which loadable polymer latexes are used in that the light fastness of the cyan image in particular is worse than that obtained when a high boiling point coupler solvent which is immiscible with water is used. Moreover, there is a further disadvantage in that large amounts of polymer must be used in order to carry enough coupler to obtain the maximum color density.
Photosensitive materials which contain a coupler dispersion (particle size of the dispersed particles from about 0.5 .mu.m to 5 .mu.m) in which an organic solvent soluble homopolymer of a hydrophobic monomer of a specified structure is used instead of a high boiling point coupler solvent and are better in terms of film properties, color reproduction failure and light fading, and in terms of their storage properties prior to processing, etc., have been disclosed in JP-B-48-30494. However, when the homopolymers of hydrophobic monomers disclosed in the aforementioned JP-B-48-30494 are used in place of a coupler solvent there are problems in that the coloring properties are poor (this is particularly marked in development baths which are essentially free of color forming accelerators such as benzyl alcohol, etc. which were added to the development baths in the illustrative examples described in the aforementioned patent) and in that the stability of the emulsion is poor.
On the other hand, copolymers with hydrophilic monomers such as acrylic acid etc. are inadequate, even though they do provide some improvement in the stability of the emulsified dispersion and the color forming properties, as there is a problem in that color fading (especially heat fading under conditions of high humidity) is adversely affected as the amount of hydrophilic monomer in the copolymer is increased in order to improve the color forming properties. Furthermore, with all of these polymers the ability to prevent crystallization of the coupler is insufficient and adverse effects also arise as a result of the formation of coupler crystals during storage of the emulsified dispersions.
Furthermore, in the case of JP-B-48-30494 (U.S. Pat. No. 3,619,195), and especially in the case of the cyan couplers, there is a major problem in that light fading is much worse (by a factor of 1.5 to 3 times) than that obtained on dispersion in a conventional high boiling point solvent (a so-called oil dispersion).
Furthermore, the hue of the cyan dye which is formed in the case of JP-B-48-30494 (U.S. Pat. No. 3,619,195) is on the long wavelength side immediately after development processing, but there is a problem in that it is liable to shift to the short wavelength side, especially on storage under high temperature conditions, which is to say that there is a problem in that the hue changes with the passage of time.
On the other hand, in cases when a polymer is emulsified and dispersed together with a coupler, the time taken to dissolve the material in an auxiliary solvent increases as the molecular weight of the polymer increases and the viscosity of the resulting solution is also raised, and so emulsification and dispersion become more difficult, coarser particles are formed and this has the effect of worsening the color forming properties, and other problems, such as a worsening of state of the coated surface, are liable to occur. Reduction of the viscosity of the solution using a large amount of auxiliary solvent in order to overcome these problems give rise to problems with the need to develop new process for treating or coating such solutions.
Improved dark fading couplers obtained in the past by changing the structure of the couplers have been opposed by inadequacies in respect of hue, color forming properties, staining or light resistance, and a new technique is clearly required. Furthermore, there are no known methods which are effective, without having an adverse effect, for improving dark fading by means of additives or by means of so-called methods of use, such as dispersion methods, etc.
On the other hand, the use of various developing agent penetrants during the color development of silver halide color photosensitive materials in which lipophilic non-diffusible (oil protected) type couplers are used has been investigated in the past with a view to increasing coloring properties and shortening processing times. Benzyl alcohol, especially when added to the color development bath, has a marked color formation accelerating effect and it is widely used at the present time with color papers, color reversal papers and color positive films which are used for display purposes, etc.
However, benzyl alcohol has a low water solubility and so a solvent such as diethyleneglycol, triethyleneglycol or an alkanolamine etc. is required to facilitate its dissolution. These compounds, including benzyl alcohol, have a high BOD biological oxygen demand) and a high COD (chemical oxygen demand), these being indicators of pollution loading, and the elimination of these compounds is desirable from the environmental protection viewpoint.
Moreover, time is required for dissolution in cases where benzyl alcohol is used, even when the above mentioned solvents are also being used, and so it is also preferable that benzyl alcohol should not be used from the viewpoint of facilitating bath preparation.
Furthermore, in cases where benzyl alcohol is carried over to a bleach bath or bleach-fix bath downstream of the development bath it can result in the formation of a leuco form of the cyan dye and this results in a reduction of the color density. Moreover, the wash-out rate of the development bath components is lowered and there are some cases where this has an adverse effect on the image storage properties of the processed photosensitive material. Hence, the use of benzyl alcohol is also undesirable from this point of view.
Thus, the development of coupler dispersions which provide improved image storage properties and which also have excellent coloring properties even when benzyl alcohol is not used is clearly desirable